Microwave phase shifter



Malh 5, 1963 D. R. DEwHlRsT 3,080,536

' MICROWAVE PHASE SHIFTER Filed Nov. 2, 1959 3 Sheets-Sheet 1 /4 23 2/ /5 Em je:

5 Sheets-Sheet 2 March 5, 1963 D. R. DEwHlRsT MICROWAVE PHASE: SHIFTER Filed Nov. 2, 1959 5 Sheets-Sheet 3 Filed NOV. 2, 1959 United States Patent O M aesasas MiCRWAVE PHASE SHEFTER Donald R. Dewhirst, Los Angeles, Calif., assigner to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Fiied Nov. 2, 1959, Ser. No. 851,213 13 Claims. (Cl. S33-24.1)

The present invention relates to a microwave phase shifter and, more particularly, to a phase shifter having a magnetic circuit of saturable ferrite material for varying the phase of propagated energy in discrete steps.

Variable phase Shifters for operation at microwave frequencies have been developed using electronically controlled ferrite elements. Such devices, in general, comprise a section of waveguide having an axially mounted ferrite element with a coil wound about the waveguide to provide an axial magnetic field through the element when current flows through the coil. A variation in the amplitude of the current flowing through the coil results in a change in the magnitude of the axial magnetic field that, in turn, alters the radio frequency permeability of the ferrite element and, thereby, the propagation constant of the microwave energy. Thus, by suitably controlling the amplitude of the current in the coil, the phase of the propagated energy may be varied in any desirable manner.

With phase Shifters of the type described in the preceding paragraph, the driving or phase-establishing current iiows continuously through the coil. Since any variation in the amplitude of the current results in a change of the established phase shift, the source of current must be extremely well regulated, which requirement is difficult and expensive to attain.

With the increased interest in electronically scanned antenna array systems, the importance of the ferrite type phase shifter has been considerably increased. As presently contemplated, such antenna arrays require many phase Shifters mounted in close proximity to each other. This fact, plus the continuous flow of current in the coils for given values of phase shift, results in the generation of considerable heat that must be suitably dissipated. That heat is a definite problem where ferrite elements are subjected thereto is readily realized in view of the rapid loss of magnetic properties by such elements as their Curie temperature is approached. Additionally, the current supply requirement for an antenna array, as discussed, is necessarily large and must be extremely stable.

Another factor to be considered with respect to such antenna systems is the necessary controller for programing the phase shifts with respect to the individual radiator elements of the array. Because it is necessary to control the required amount of current to each of the phase Shifters, a complex computer is required.

It is, therefore, an object of the present invention to provide a new and improved microwave phase shifter.

Another object of the invention is to provide a microwave phase shifter wherein incremental phase shifts are accomplished by short duration pulses of current through suitably mounted driving coils for controlling the radio frequency permeability of a phase shifting element.

Still another obje-ct of the invention is to provide a microwave phase shifter having a saturable magnetic circuit including the phase shifting element of square loop magnetization characteristic, so that selective saturation of branches of the magnetic circuit results in altered values of phase shift.

A further object of the invention is to provide a microwave phase shifter having a multiwbranch, saturable magnetic :circuit of square loop magnetization characteristic for controlling the magnetization of a phase shifting element by selective saturation of portions of the magnetic circuit.

3,080,536 Patented Mar. 5, 1953 To achieve the foregoing objects and overcome the disadvantages of known types of phase Shifters, there is provided in accordance with the present invention a section of waveguide for propagating microwave energy with an axially disposed magnetic phase shifting element suitab-ly mounted in the waveguide. A saturable magnetic circuit including the magnetic phase shifting element is provided with at least two branches external to the waveguide.

Preferably, the material of the magnetic circuit saturates at a low value of magnetic iielid and has a square loop magnetization characteristic with the sum of the residual magnetism of the outer branches being substantially equal to that of the phase shifting element. A first coil is wound about the waveguide so that a pulse of current therethrough causes magnetic saturation in one direction of the entire magnetic circuit and thereby a selected value of phase shift of the propagated energy. A second coil is wound about one of the outer branches and a subsequent pulse of current is applied to drive this branch to magnetic saturation in the opposite direction. Magnetism of the phase shifting element then becomes minimum and there is little phase shift of the propagated energy. By adding more external branches to the magnetic :circuit with a coil on each branch and with the same relationship established with respect to the residual magnetisms of the various branches of the magnetic circuit, the number of increments of phase shift is increased in an exponential manner..

Other objects and advantages of the present invention will be readily apparent from the following description and claims considered together with the accompanying drawings, wherein like reference numerals refer to like elements, and in which v FIGURE l is a perspective view of one embodiment of the present invention;

FiGURE 2 is a longitudinal cross section of the invention of FiGUR-E 1l;

FIGURE 3 is a longitudinal cross section of another embodiment of the present invention;

FIGURE 4 is a longitudinal cross section of 'another embodiment of the present invention;

FlGURE 5 is an end view of the embodiment of FIG. 4; and

FiG-URE 6 is a longitudinal cross section Yof other embodiment of the present invention.

Referring now to the drawing, FiG'URE l in particular, a section lof rectangular waveguide 11 is provided for propagating microwave energy in the dominant TEM) mode from a source (not shown) suitably coupled to an input end 12 toward an output end 13. To shift the phase ofthe pnopagated energy, an elongated ferrite element 14 of rectangular planar and cross sectional dimensions is suitably mounted along the longitudinal axis of the waveguide 11 with a broad dimension extended parallel to narrow walls of the waveguide and transverse to the broad walls thereof.

As may be seen more clearly in FIGURE 2, a closed magnetic circuit 16 includes the phase shifting -ferrite element 14 as a central branch member. Such magnetic circuit 16 also includes two similar outer branches 17 and 18, respectively, spaced from and in parallel alignment with the phase shifting element 14 -and the respective broad walls of the waveguide 11. To substantially overcome the impedance mismatch resulting from the insertion of element 14 in the waveguide 11, blocks 19 of ferrite material having pointed tapered portions are mounted at either end of the element. As illustrated in FiGURE 1, the tapered blocks 19 have the same width dimension as element 14 at lthe junction therebetween and extend the entire narrow dimension of the waveguide 11. To complete the magnetic circuit 16, ferrite spacers 21 still an- 3 are extended through Suitable apertures 22 in the broad walls of the waveguide 11 between the tapered blocks 19 and the extremities of the respective -outer branches 17 and 18. The material of the elements 14, 17, 18, 19 and ,21 in 'the magnetic circuit is preferably ferrite with a low value of magnetic saturation and with a square loop magnetization characteristic.

To prevent loss by radiation through the ferrite filled apertures 22, a thin layer of conductive material 29,

Ysuch as silver paint, is disposed between the contact area of the blocks 19 and 21 as a continuation of the inner surface of the broad walls of the waveguide 11. It is to be noted that for fast pulsing techniques with respect to the two coils 23 and 24, fthe waveguide 11, in the area of the coils, may be thin walled or plastic with a thin inner coating of conductive material. This latter provision decreases a single short circuited winding effect of the waveguide walls and permits the use of fast current pulses.

In accordance with the present invention, the dimensions of the outer branches 17 and 18 are correlated with those 'of element 14 so that the residual magnetism of the outer branches is substantially equal and the sum thereof substantially equal to the residual magnetism of the inner branch or phase shifting element 14. Under these circumstances ther output of the first pulsed power supply 26 is connected by the switch 25 to the first coil `23 to provide a pulse of current having an amplitude suliicient to develop arsaturat-ing magnetic field in one direction through the entire magnetic circuit 16 as in-dicated by solidV lines 31 of FIGURE 2. Becau-se of the magnetization characteristic of the magnetic circuit 16, the residual magnetism remaining after the pulse has terminated is close to the saturation value and remains to .magnetization of the other outer branch 18 of the magnetic circuit 16. Thus, since the residual magnetism of t-he outer branches 17 and 13 are equal and opposite, the net magnetic field through the phase shifting element 14 is zero and the microwave energy propagates through the waveguide 11 with minimum phase shift.

Referring now to the embodiment of the invention illus-V trated'in FIG. 3, it is to -be notedthat the entire structure of FIGS. l and 2 is .included therein. In addition to the basic structure of the latter figures, twoy more branches 41 and 43 are included in the magnetic circuit 16 with the branches being mounted parallel to and in alignment with the other branches 14, 17 and 18. Preferably, the two branches 41 and 43 are disposed adjacent to the branch 17 having the second coil 2,4 wound thereon and are spaced apart -by spacers 21 with such spacers completing and closing the magnetic circuit Y16.

'lio magnetically satunate the branches 41 and 43 in a direction opposite to the original saturation Yof the magnetic circuit 16 provided by the first coil 23, as previously discussed, separate coils 46 and 47 are respectively wound on the additional branches. Energization of the coils 46 and 47 is respectively providedrby separate combinations of switches 51 and 52 [and third and fourth pulsed power supplies 53 and 54 connected to such coils.

Again, the entire magnetic circuit 16 is of a material that has a low value of magnetic saturation and a square loop magnetization characteristic. The dimensions ofthe outer bnancnes 17, 41 and 43 having coils 24, 46 and 47 wound thereon, are selected to provide a residual magnetism equal to the residual magnetism of the other outer branch 18 and the sum of such residual magnetisms is equal to that of the phase shifting element 14.

With the foregoing conditions satisfied the embodiment of FIG. 3 operates in the same manner as that discussed in the description of FIGS. l and 2 to provide a greater number of .phase shifts of the propagated energy. Thus', after magnetic saturation of the entire magnetic circuit 16 in one direction by energizaton of the first coil Z3 to establish a maximum value of phase shift, the other coils 24, 46 and 47 are selectively energized, singly or in combination, to develop lesser values of phase shift by saturation of the respective branches 17, 41 and 43 in the opposite direction. In such manner a greater number of phase shifts is obtained thanthere are branches in the magnetic circuit 16.

Another embodiment of the invention is illustrated in FIGS. 4 and 5 and includes the structure described with respect to the embodiment of FIG. 3. Thus, in addition to the two outer branches 41 and 43,y two more branches 61 and d2 have been mounted on the -other side lof the waveguide 11 in parallel alignment with the previously described bnanches. VThese latter branches 46-1 and 62 are also connected to the magnetic circuit 116 by spacers 21. As in the previously described embodiments the material of the entire magnetic circuit 16 has a low value of magnetic saturation and a square loop magnetization kcharacteristic.

In accordance with this embodiment of the invention coils 66, 67 and 68 are respectively ywound about the three branches 18, 61 and 6-2'and respectively connected to combinations of switches 711,72 land y713 and fifth, sixth and seventh pulsed power supplies 76, 77 and/78 (see FIG. 5). Also, the residual magnetism of the outer branches 17, 41 and 43 on one side of the waveguide 11 is equal to the residual magnetismof the outer branches 1S, l61 and 62 on .the opposite side of the waveguide and the sum of the residual magnetism of all 4of the outer branches is equal to that of the phase shifting element 14.

When lthe first coil Z3 is energized the entire magnetic circuit 16 is magnetically saturated in one direction and the residu-al magnetism of the phase shifting element 14 results in a maximum value of phase shift of the microwave energy propagated through waveguide 11. Thereafter, by selective energization of lthe coils on the outer branches of .the magnetic circuit 16, the branches affected are magnetically saturated in the opposite direction to varyrthe net magnetization of the phase shifting element 14 in the same manner as previously described with respect to the invention of FIG. l. With coils on each of 'the outer .branches of the magnetic circuit y16, in accordance with this embodiment of the invention, the number of phase shifts possible is equal to 2".-1 where n is the .number of branches `of the magnetic circuit. From this it is .seen that, as the number of branches is increased, the number of possible phase shifts is increased exponentially to provide a much greater number of phase shifts than there are branches. Y

Referring -now to FIG. 6 of the drawing, there is Vshown a further embodiment of the present invention by way'of illustrating modifications/that may be made within the scope of the invention lof FIGS. l-S.V Thus, there is provided a central section of reduced height rectangular waveguide 101 with two multiple step, Yquarter wave impedance matching transformer sections 102 and 103 extended from either end toV couple to standard size waveguide (not shown). A phase shifting element `104 having a rectangular configuration is mounted along the longitudinal center line of the central section transversely between the broad walls. It is to be noted that in this embodiment the phase shifting element i104 contacts both broad walls of the central section of waveguide 1011 and, thereby, reduces the heat dissipation problem in that heat generated in the element is conducted away and radiated from the waveguide walls.

In addition to the stepped end sections 102 and 103 for impedance matching purposes, tapered elements 105 and 107 are mounted with one at either end of the phase shifting element 104 as continuations thereof. These tapered elements 106 and 107 may be of the same material as the phase shifting element, to be set forth hereinafter, -or may be of a dielectric material, such as stycast.

Apertures 108 extend through the broad walls of the central section of waveguide 101 at either extremity of the phase shifting element 104 and receive spacers 109 that contact the phase shifting element with a portion of each extending externally of the waveguide. As described with respect to the other embodiments, a thin layer 111 of conductive material, such as silver paint, is disposed between each of the spacers 109 and the phase shifting element 104 to prevent loss of the propagated energy by radiation. The spacers 109 extend outwardly from the central section 101 and serve as mountings for two oppositely disposed parallel branches 112 and -113 with sufficient space between the branch 112 and the adjacent waveguide Wall to receive windings .of two coils i114 and 116 therebetween. One coil 114 is suitably wound about the central section 101 of waveguide between the spacers 109 and is connected to a source (not shown) of current pulses, similar to that indicated for .the device of FIG. l. The other coil 116 is wound about one of the branches 11:2 and is connected to a separate source of current pulses (not shown), also, similar to that indicated for the device of FIG. l.

With the phase shifting element 104, the spacers 109, and the -two branches 1.12 and 11S all being of the same ferrite material having a low value of magnetic saturation, such described structure provides a closed magnetic oircuit. Also, in accordance with this embodiment of the invention, the dimensions of the two outer branches 112 and 113 are selected to have the same value of residual magnetism with the sum of the two residual magnetisms being equal to the residual magnetism of the phase shifting element 104.

With the foregoing structural relationships and conditions, the device .of this embodiment `operates in the same manner as set forth with respect to the embodiment of FIG. l. Thus, by applying a pulse of `current to coil 114 the entire magnetic circuit is magnetically saturated Iin `one direction to provide a maximum value of phase shift to the propagated microwave energy by the action of the residual magnetism of the phase shifting element 104. Thereafter, by applying a pulse of current to `the coil 116 of the branch 112, this branch of the magnetic circuit is magnetically saturated in the opposite direction to `reduce the residu-al magnetism of the phase shifting element 104 to zero land thereby return the phase of the microwave energy to the minimum value. It is to be noted that the magnetic circuit illustrated and described with respect to FIG. 6 may be readily changed to provide the type of operation described with -respect -to FIGS. 1 5.

Thus, there have been described in the foregoing phase Shifters wherein the phase shifting operation has been accomplished by pulses of current flowing through coils in a selective manner rather than a continuous flow of such current as was previously required. The need for regulation of the amplitude of the current for each value of phase shift has thereby been obviated. For accurate control of -a plurality of phase Shifters in a single system, the complexity of the required computer type of controller is considerably lessened with the devices of the present invention.

While the salient features of the present invention have been shown and described with respect to several embodiments of the invention, it will be readily apparent that numerous modifications may be made within the spirit and scope of the invention and it is therefore not desired to limit the invention to the exact details shown and described, except as they may be set forth in the following claims.

What is claimed is:

l. In a microwave phase shifter, the combination ccmprising a section of waveguide having a longitudinal axis, a closed magnetic circuit of ferrite material saturating at a substantially low value of magnetic field, said magnetic circuit including a phase shifting element disposed within said waveguide and along said axis, said magnetic circuit further including a plurality of parallel and aligned branches, means included with said magnetic circuit for establishing magnetic saturation of the entire magnetic circuit in one direction to provide a maximum value of phase shift of propagated microwave energy, and means also included with said magnetic circuit for selectively `establishing magnetic saturation of said branches in an opposite direction to alter the magnetization of said phase shifting element and establish lesser phase shifts of said energy.

'2. In a microwave phase shifter, the combination comprising a section of waveguide having a longitudinal axis, a closed magnetic circuit of ferrite material saturating at a substantially low value of magnetic field, said magnetic circuit including a phase shifting element disposed within said waveguide and along said axis, said magnetic circuit further including a plurality of parallel and aligned branches, a principal coil wound about said waveguide in the vicinity of said phase shifting element means coupled to said principal coil for applyiig a current pulse to magnetically saturate said magnetic circuit in one direction to'provide a maximum value of phase shift of propagated microwave energy, secondary coils wound on selected branches, and means coupled to said secondary coils for selectively applying current pulses to magnetically saturate said branches in an opposite direction to alter the magnetization of said phase shifting element and establish selectedlesser values of phase shift of said energy.

13.I In a microwave phase shifter, the combination comprising a section of waveguide having a longitudinal axis; an elongated ferrite phase shifting element mounted along said axis within said waveguide; a plurality of ferrite branch elements disposed external to said waveguide in parallel and aligned relation with said phase shifting element; ferrite spacer elements disposed between extremities of said phase shifting element and adjacent branch elements through apertures in the Walls of said waveguide; said ferrite material of each of said ferrite elements saturating at a low value of magnetic field; a prinwaveguide in the vi said phase shifting element; meanbs coupled to szicrlutiii'iii cipal coil for applying a pulse of current to magnetically saturate said phase shifting element, said spacers and said branch elements in one direction to provide a inaximum value of phase shift of propagated microwave energy; secondary coils wound on selected branch elements' and means coupled to said secondary coils for selectively applying pulses of current to magnetically saturate said branch ele`ments in an opposite direction to alter the magnetization of said phase shifting element and establish selected lesser values of phase shift of said energy.

4. In a microwave phase shifter, the combination comprising a section of rectangular waveguide having a longitudinal axis, a closed magnetic circuit of ferrite material saturating at a substantially low value of magnetic field, said magnetic circuit including a phase shifting element disposed within said waveguide and along said axis, said magnetic circuit further having a plurality of parallel and aligned branchesfsaid plurality of branches being disposed externally of said waveguide, said externally d1sposed branches being divided in quantity and grouped on opposite sides of said waveguide, said branches being dimensioned to provide equal values of residual magnetism on either of said opposite sides of said waveguide with the sum of the residual magnetism of such external branches being equal to that of said phase shifting element, means inciuded with said. magnetic circuit for establishing magnetic saturation of the entire magnetic circuit in one direction to provide a maximum value of phase shift of propagated microwave energy, and means also included with said magnetic circuit for selectively establishing magnetic saturation of said branches in an opposite direction to alter the magnetization of said phase shifting element and establish lesser phase shifts of said energy. v

.5. In a microwave phase shifter, the combination comprising a section of rectangular waveguide having a longitudinal axis, a closed magnetic circuit of ferrite material saturating at a substantially low value of magnetic field, said magnetic circuit having three parallel and aligned branches with the center branch being disposed along said axis within said waveguide and the outer branches respectively disposed externally of said waveguide in spacedapart relation with opposite walls thereof, said branches being dimensioned to provide equal values of residual magnetism with the sum of the residual magnetism of such outer branches being equal to that of said center branch, means included with said magnetic circuit for establishing magnetic saturation of the entire magnetic circuit in one direction to provide a maximum value of phase shift of propagated microwave energy, and means also included with said magnetic circuit for selectively establishing ymagnetic saturation of one of said outer branches in an opposite direction to alter the phase shift of propagated microwave energy between a maximum and a minimum value.

6. In a microwave phase shifter, the combination comprising a section of rectangular waveguide havingra longitudinal axis; a phase shifting element mounted along said axis in said waveguide; a pair of branch elements disposed in parallel alignment, with each other and with said phase shifting element, external to said waveguide with such elements positioned adjacentropposite sides thereof; yspacer elements extended through apertures in walls of said waveguide to contact said phase shifting element and said branch elements at extremities thereof, said spacer elements supporting said branch elements away from walls of said waveguide; Ysaid phase shifting element, branch elements, and spacer elements being a ferrite material saturating at a substantially low value of magnetic field; a first coil wound about said waveguide between said spacer elements; means coupled to said rst coil for'applying a pulse of current to magnetically saturate all of said ferrite material in one direction and provide a maximumY value of phase shift of propagatedY microwave energy; a second coil wound on one of said branch elements; and means coupled to said second coil for applying a pulse of current to magnetically saturate said one branch element in an opposite direction; said waveguide, said externally disposed branches being divided inV quantity` and grouped with a single branch on one side of said waveguide and the others on an opposite side thereof, said branches being dimensioned to provide equal values of residual magnetism on either of said opposite sides of said waveguide with the sum of the residual magnetism of such external branches being equal to that of said one branch within said waveguide, means included with said magnetic circuit for establishing magnetic saturation ofthe entire-magnetic circuitrin one direction to provide a maximum value of phase shift of propa-V gated microwave energy, and means also included with said magnetic circuit for selectively establishing magnetic saturation of said outer branches other than said single branch in an opposite direction to alter the magnetization of said one branch in said waveguide and establish lesser phase shifts of said energy. 'Y

8. In a microwave phase shifter, Ythe combination comprising a section of rectangular waveguide having a longitudinal axis; a phase shifting element mounted along said axis in saidwaveguide; a plurality of branch elements disposed in parallel alignment, with eachother and with said phase shifting element, external to said waveguide with a single branch element on one side of said waveguide and the remainder'on an opposite side thereof;

t spacer elements disposed between adjacent ones of said branches and extended through apertures in walls of said waveguide to contact said phase shifting element at exe tremities thereof, said spacer elements supporting said branch elements away from walls of said waveguide and from adjacent branches; said phase shifting element, branch elements, and spacer elements being of a Vferrite material saturating atV a substantially low value of magnetic field; a first coil wound about said waveguide between said spacer elements; means coupled to said rst coil for applying a pulse of current to magnetically saturate yall of said ferrite material Vin one direction and provide a maximum value of Yphase shift of propagated microwave energy; a plurality of second coils respectively wound on said plurality of branchelements except said single branch element; land means selectivelycoupled to said second coils for applying a pulse of current to magnetically saturate respective branch elements in an opbranch elements being dimensioned to have equal valuesY of residual magnetism with the sum of such residual magnetisms being equal to the residual magnetism'of said v phase shifting element, whereby the phase of propagated` energy may -be switched between maximum and minimum values.

7. In amicrowave phase shifter, the combination comprising a section of rectangular waveguide having a longitudinal axis, a closed magnetic circuit of ferriteV material saturating at a substantially low value of magnetic field, said magnetic circuit havingV a plurality of parallel and aligned branches with one branch being disposed along said axis within said waveguide and the remainder'of said plurality of branches being Vdisposed externallyV of said posite direction; said branch elements being dimensioned to provide, equal valuesyof residual magnetism von either side of said waveguide with the sum of such residual magnetism being equal to the residual magnetism of said phase shifting element.

9. In a microwave phase shifter, the combination corn-Y prising a section of rectangular waveguide having a longitudinal axis, a Vclosed magnetic circuit of ferrite material saturating at a substantially low value of magnetic field, said magneticrcircuit including a ,phase shifting element disposed within said waveguide .and along said axis, said magnetic circuit further having a plurality of parallel and aligned branches, said plurality of branches Vbeing disposed externally of said waveguide with an equal quantity on opposite sides thereof, said branches being dimensioned to provide equal values of residual magnetism on either of said opposite sides of'said waveguide with the sum of the residual magnetism of such -external branches being equal to that of said phase shifting element means includedrwith said Amagnetic circuit Yfor establishing magnetic saturation of the entire magnetic circuit in one direction to provide a maximum value of phase shift of 'propagated microwave energy, and separate means included with each of said external branches for selectively establishing magnetic saturation ofselected quantitiesof said external branchesin an opposite direction to alter Vthe magnetization of said phase Yshifting element.

l0. In a microwave phase shifter, the combination comprising a section of rectangular waveguide having a longitudinal axis; a phase shifting element mounted along said axis in said waveguide; a piurality of branch'elements disposed in parallel alignment, with each other and with said phase shifting element, external to said waveguide with an equal quantity on opposite sides of said waveguide; spacer elements disposed between adjacent ones of said branches and extended through apertures in walls of said waveguide to contact said phase shifting element at extremities thereof, said spacer elements supporting said branch elements away from walls of said waveguide and from adjacent branches; said phase shifting element, branch elements, and spacer elements being of a ferrite material saturating at a substantially low value of magnetic field; a first coil wound about said waveguide between said spacer elements; means coupled to said first coil for applying a pulse of current to magnetically saturate all of said ferrite material in one direction and provide a maximum of phase shift of propagated microwave energy; a plurality of second coils respectively wound on said plurality of branch elements; and means selectively coupled to said second coils for applying a pulse of current to magnetically saturate respective branch elements in an opposite direction; said branch elements being dimensioned to provide equal values of residual magnetism on either side of said waveguide with the sum of such residual magnetism being equal to the residual magnetism of said phase shifting element.

l1. In a microwave phase shifter, the combination comprising a section of reduced height rectangular waveguide having a longitudinal axis and multiple-step impedance matching waveguide sections extended from either end for coupling to standard waveguide, a closed magnetic circuit of ferrite material saturating at a substantially low value of magnetic field, said magnetic circuit including a phase shifting element disposed within said reduced height section of waveguide and along said axis, said magnetic circuit further having a plurality of parallel and aligned branches, said plurality of branches being disposed externally of said waveguide with a selected quantity on opposite sides thereof, said branches being dimensioned to provide equal values of residual magnetism on either of said opposite sides of said waveguide with the sum of the residual magnetism of such external branches being equal to that of said phase shifting element, means included with said magnetic circuit for establishing magnetic saturation of the entire magnetic circuit in one direction to provide a maximum value of phase shift of propagated microwave energy, and separate means included with each of selected external branches for selectively establishing magnetic saturation of selected quantities of said external branches in an opposite direction to alter the magnetization of said phase shifting element.

l2. In a microwave phase shifter, the combination comprising a section of reduced height rectangular waveguide having a longitudinal axis and multiple-step impedance matching waveguide sections extended from either end for coupling to standard size waveguide; a phase shifting element mounted along said axis in said reduced height section of waveguide; a plurality of branch elements disposed in parallel alignment, with each other and with said phase shifting element, external to said reduced height section of waveguide with said branch elements being divided in quantity and disposed 4on opposite sides of such waveguide section; spacer elements disposed between adjacent ones of said branches and extended through apertures in walls of said waveguide to contact said phase shifting element at extremities thereof, said spacer elements supporting said branch elements away from walls of said waveguide and from adjacent branches; said phase shifting element, branch elements, and spacer elements being of a ferrite material saturating at a substantially low value of magnetic field; a first coil wound about said waveguide between said spacer elements; means coupled to said rst coil for applying a pulse of current to magnetically saturate all of said ferrite material in one direction and provide a maximum value of phase shift of propagated microwave energy; a plurality of second coils respectively wound on said plurality of branch elements; and means selectively coupled to said second coils for applying a pulse of current to magnetically saturate respective branch elements in an opposite direction; said branch elements being dimensioned to provide equal values `of residual magnetism on either side of said waveguide with the sum of such residual magnetism being equal to the residual magnetism of said phase shifting element.

13. In a microwave phase shifter, the combination comprising a section of waveguide having a longitudinal axis; a closed magnetic circuit of ferrite material including a phase shifting element disposed within said waveguide and along said axis, said magnetic circuit further including a branch element disposed externally to said waveguide; means for establishing magnetic saturation of the entire magnetic circuit including said phase shifting element in one direction to provide maximum phase shift of the propagated microwave energy; and further means for establishing at will magnetic saturation of said branch in an opposite direction to reduce the 4magnetization of said phase shifting element, thereby producing a smaller phase shift of said energy.

References Cited in the le of this patent UNITED STATES PATENTS 2,850,705 Chat et al. Sept. 2, 1958 UNITED STATES PATENT oEEICE CERTHHCATE OF CORRECTHMN Patent No. 3O80,536 March 5 1963 Donald R Dewhrst vIt is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6q lne 36{ after "element" insert a Comma; line 37, for "applylg" read applying column 8, line 62, after "element" insert a commao Signed and sealed this 22nd-day of October 1963o SEAL) nest:

{NEST W. SWIDEE l l ttesting Officer AC ting Commissioner of Patents UNITED STATES PATENT oEETCE CERTIFICATE OF CORRECTION Patent No. 3,080,536 March 5 1963 Donald R0 Dewhirst error appears in the above `numbered patlt is hereby certified that t the said Letters Patent should read as ent rec'1 'iiri1'1gg,` correction and tha corrected below.

Column 6g line 36, after "element" insert a comma; line 3'?9 for "applyiig" read applying column 8, line 62, after "element" insert a oomma Signed and sealed this 22nd -day of October 1963D SEAL) tteStI EDWM LW REYNOLDS NEST W. SWIDER A C t i ng Commissioner of Patents ttesting Officer 

1. IN A MICROWAVE PHASE SHIFTER, THE COMBINATION COMPRISING A SECTION OF WAVEGUIDE HAVING A LONGITUDINAL AXIS, A CLOSED MAGNETIC CIRCUIT OF FERRITE MATERIAL SATURATING AT A SUBSTANTIALLY LOW VALUE OF MAGNETIC FIELD, SAID MAGNETIC CIRCUIT INCLUDING A PHASE SHIFTING ELEMENT DISPOSED WITHIN SAID WAVEGUIDE AND ALONG SAID AXIS, SAID MAGNETIC CIRCUIT FURTHER INCLUDING A PLURALITY OF PARALLEL AND ALIGNED BRANCHES, MEANS INCLUDED WITH SAID MAGNETIC CIRCUIT FOR ESTABLISHING MAGNETIC SATURATION OF THE ENTIRE MAGNETIC CIRCUIT IN ONE DIRECTION TO PROVIDE A MAXIMUM VALUE OF PHASE SHIFT OF PROPAGATED MICROWAVE ENERGY, AND MEANS ALSO INCLUDED WITH SAID MAGNETIC CIRCUIT FOR SELECTIVELY ESTABLISHING MAGNETIC SATURATION OF SAID BRANCHES IN AN OPPOSITE DIRECTION TO ALTER THE MAGNETIZATION OF SAID PHASE SHIFTING ELEMENT AND ESTABLISH LESSER PHASE SHIFTS OF SAID ENERGY. 